1. Field of the Invention
The present invention relates to methods and devices for reinforcing dysfunctional heart valves and other body structures. More specifically, embodiments of the present invention relates to using an aortic valve prosthesis to treat a diseased aortic valve annulus.
2. Description of the Related Art
The circulatory system of mammals includes the heart and the interconnecting vessels throughout the body that include both veins and arteries. The human heart includes four chambers, which are the left and right atrium and the left and right ventricles. The mitral valve, which allows blood flow in one direction, is positioned between the left ventricle and left atrium. The tricuspid valve is positioned between the right ventricle and the right atrium. The aortic valve is positioned between the left ventricle and the aorta, and the pulmonary valve is positioned between the right ventricle and pulmonary artery. The heart valves function in concert to move blood throughout the circulatory system. The right ventricle pumps oxygen-poor blood from the body to the lungs and then into the left atrium. From the left atrium, the blood is pumped into the left ventricle and then out the aortic valve into the aorta. The blood is then recirculated throughout the tissues and organs of the body and returns once again to the right atrium.
If the valves of the heart do not function properly, due either to disease or congenital defects, the circulation of the blood may be compromised. Diseased heart valves may be stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, and/or incompetent, wherein the valve does not close completely. Incompetent heart valves cause regurgitation or excessive backward flow of blood through the valve when the valve is closed. For example, certain diseases of the heart valves can result in dilation of the heart and one or more heart valves. When a heart valve annulus dilates, the valve leaflet geometry deforms and causes ineffective closure of the valve leaflets. The ineffective closure of the valve can cause regurgitation of the blood, accumulation of blood in the heart, and other problems.
Aortic stenosis and aortic regurgitation are common diseases in an aging population. An effective therapy for these conditions is aortic valve replacement, in which damaged leaflets are excised and the diseased valve is sculpted to receive a replacement valve. Aortic valve replacement is usually accomplished by a surgical procedure, although endovascular procedures for valve replacement are an alternative. One endovascular procedure, percutaneous aortic valve replacement, is becoming a reality and brings new hope for a number of patients who cannot currently be treated with traditional surgical techniques.
Although surgical valve replacement concerns about 200,000 patients worldwide every year, it is estimated that up to two thirds of these patients do not receive surgery due to either excessive risk factors and comorbidities or patient refusal due to fear of lifestyle changes following heavy surgery in elderly patients. The size of this untreated population is expected to increase because of the aging population. Without replacing the valve, aortic stenosis is associated with a very high mortality rate (50 to 60% at one year) beyond the onset of symptoms. A percutaneous valve may bring a less invasive therapeutic solution for these patients.
Although a number of minimally invasive techniques for replacing heart valves do exist, they are often problematic. For example, with many minimally invasive valve replacements, paravalvular leaks can occur, with moderate to severe leakage occurring in 25% of cases. Paravalvular leakage may be due to sub-optimal implant size, shape, location, and the amount of morphology or calcification. These calcified lesions are extremely difficult to remove without fragmentation and without leaving some pieces of calcium, which may migrate and embolize. Accurate and secure deployment of the valve prostheses will remain a significant issue for these endovascular procedures.
The amount of reshaping or adjustment of the implants is important in these procedures. Excessive oversizing could cause reshaping of the valve annulus, but could reduce the likelihood of paravalvular leaks. The resultant paravalvular leak is somewhat unpredictable at the time of the implantation.